I hate to be posting repair questions, but my car is suicidal.

Today was amazingly hot and humid. I put on my a/c and drove to my destination. Half way there my A/C was barely blowing cold air.

My temperature indicator showed just less than 100C. After turning off the car I wanted to see how hot it was under the hood. The heat was incredible. Everything within the engine compartment was far too hot to touch, even the body panels.

The engine fans turn and the auxiliary fan was on all day.

Is something in needing of repair or should I focus on additional radiators or something?

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1984 300D / The only Benz I have

Completed weekend projects

1. R/R front crankshaft seal
2. R/R nearly the whole vacuum system
3. Converted to WVO www.greasemachine.com
4. Upgraded to electric power locks
5. Upgraded and rewired stereo/amp/speakers
6. Installed 2.88 differential

Tons of posts on the forum regarding this subject. Have fun searching the different opinions.

My two cents is that you can spend a great deal of time and energy obsessing over the issue without much results. I was unable to bring my operating temp down (similar to yours) and eventually just lived with it. Nothing ever came of it.

If all the fans and cooling systems appear to be functioning, I think we're just victims of this unique MB quirk.

dp

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DAILY DRIVERS:
'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)

SOLD:
'82 240D 229k (Matt's - Converted-300DT w/ 4 speed

100C is ok on a hot day. As long as you were not near the temp. red line, my owner's manual states that it is OK and will happen. You may want to have your sensor checked, however, just to be sure that you are getting the correct temp. reading. Do you have R134 in your AC? ( Get ready for a hundred different opinions. )

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Paul 1987 300 SDL; 2000 ML; '69 MGB; '68 VW Fastback

I have a different perspective of the 617 now that I have the SDL.

The 603 can warm itself up to 100°C. when under moderate boost, with the a/c off.

However, with the a/c on, it will have a difficult time getting over 105°C. even on a long upgrade.

So, look at the situation this way:

The 603 has no issues at 105°C. and it has an aluminum head.

Therefore, all you folks with 617 engines can relax and worry about other things. You can probably run the 617 up to 120°C. if you have proper coolant and sufficient pressure in the cooling system.

Keep in mind that the coolant at a temperature of 100C is right at the boiling point of water at atmospheric pressure. Other metal parts of the engine will be hotter in normal operation.

Engine oil is expected to run about 100C so that moisture will boil away, so the valve cover will be at 80C or so.

Heat under the hood is normal, and as human beings we are always impressed with normal underhood temperatures, since we cannot relate to them properly in our normal skin...

Best Regards,
Jim

I have an '83 300D with 243K on the clock. It had 193K when I first bought it, and it ran cold (barely 80 degrees celsius in the Florida summer). After a new radiator, thermostat, fluid, etc., my temp gauge now reads at around 100 degrees celsius. However, I wanted to see for myself if it was really running at 100, so I brought it to my dad's firehouse and he put an IR or laser heat gun on it in various places where it would be hottest, and the warmest temp we found was 187 degrees farenheit when warmed up (about 86 degrees celsius) - so I know I'm getting readings about 14 degrees celsius wamer than what it is running. If you have access to a IR or laser heat gun, do it - you might be surprised.

I have see a product called Water Wetter, that is suppose to lower the temp in the engine by 10-20°F. They have one for gassers and one for diesels. I havent heard anything bad about the stuff yet, and was thinking of trying it myself.

You can check it out here:
http://www.redlineoil.com/products_coolant.asp?productID=70

If anyone has any input on the stuff from first, second or any hand experience please advise.

__________________
1980 300D European
"The Red Fox"
200,000 miles

2003 Chevrolet Silverado

609 Certification

Damn, I had hoped people were not going to say "this is just how my car runs"



It is R134A
Should I go back to R12 I'll pay 25 bucks a pound if it works.

__________________
1984 300D / The only Benz I have

Completed weekend projects

1. R/R front crankshaft seal
2. R/R nearly the whole vacuum system
3. Converted to WVO www.greasemachine.com
4. Upgraded to electric power locks
5. Upgraded and rewired stereo/amp/speakers
6. Installed 2.88 differential

Down in Texas, for the summer, I would be interested in seeing the result of running the 617 with no thermostat.

In this situation, the engine will stabilize at about 65°C. and will only climb if under heavy load or when it has reduced airflow. Starting off at 65°C. instead of 80°C. will give you that much more margin in terms of time.

You could leave it out all summer and report back on how it did for you.

I'm very sure that we would be interested in the results, and, additionally, if it still gets up to 100°C.

I figured the thermostat was wide open.

If you think it will help that bastards getting pulled Tuesday.

__________________
1984 300D / The only Benz I have

Completed weekend projects

1. R/R front crankshaft seal
2. R/R nearly the whole vacuum system
3. Converted to WVO www.greasemachine.com
4. Upgraded to electric power locks
5. Upgraded and rewired stereo/amp/speakers
6. Installed 2.88 differential

There is nothing wrong with your car, it is running fine. Under 100c is normal, that's the way mine runs on a 60 degree day. Check your owner's manual, page 12, quote "Up to red marking: Maximum permissible temperature" and on page 58 it elaborates: "If the antifreeze mixture is good to -30c/-22f, the boiling point of the coolant in the pressurized cooling system of your vehicle is approx. 125c/257f.

During severe operating conditions and stop-and-go city traffic, the coolant temperature must not rise above the red marking"

So your car is perfect, you don't need to do anything. Unless you think you know more about it than the people who designed and built your car.

Removing the thermostat or doing other modifications will do more harm than good.

Removing the thermostat in Texas for the summer will do no harm.

I believe that the engine will take longer to get to 100°C.

Dr. Bert has run the 617 in similar conditions and is quite pleased with the results. You can do a search on his name and read about it, if you wish.

Please, please report back as to exactly what that temperature needle reads when the ambients get above 90°F.

Removing thermostat is common practice here in India, especially in European origin diesels, the Japanese diesels never run anything over 80c and if they do, it is trouble with capital T.

Most OM 616 used in commercial LCV app would not only remove the thermostat, they would remove the radiator cap as well, according to them, it is the only effective way to keep it cool when loaded with 5 tons of goods.

My OM 616 turbo never goes a shade over 85c and that in a 45c outside weather day. I just wont feel comfortable at 100c as I know how high the hot spots inside the engine are by then, also it is like a psychological barrier once you cross 100c, overheating is on its' way. The turbo OM 616 is equipped with a 72c thermostat and I saw a big drop in temps when I modified the air intake to a ram air system as well a removed the muffler.

It is different approach I guess, I drive my brother's Toyota diesel SUV which never goes over 80c, fully loaded with a/c on at around 45c and yet, any MB diesel at that situation is showing the dreaded temp creep.

I have used Watter Wetter when I used to live in NY with my 240D as well as Accord V6, did not see any adverse reaction except for gelling inside the radiator which made me a bit nervous.

i never tried taking out a thermostat in a 617 but as i look at the diagram of the thermostat in my opinion it would cause additional heat to build up.thermostat is open to recirculate the block only when cold and as it heats the spring is compressed and finally closes the block port when hot and allows pressure to force coolant thru the radiator.
larry perkins
72 old cars

Mine hovers just below the 100C degree mark no matter what the temp. It can be below freezing or approaching 100F as it has been the past few days and it still stays rock solid at around 97C. The only time I've ever seen it break 100C is when i was installing my veg conversion and didn't fill it up quite enough. There was still coolant visible in the expansion tank but just barely. Even then it only broke the mark while driving 75 down the highway for about 15 minutes, and even then it was only about a needle's width over. Adding the proper amount of coolant fixed it. My brother has an 84 300D that a p/o modified so that the aux fan would run all the time. If I remember correctly his runs about 90C. Both cars appear to do fine at these temps.

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Seth

1984 300D 225K
1985 300D Donor body
1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!!
1980 300SD 311K My New Baby.
1979 BMW 633csi 62K+++? Dead odo